1. Field of the Invention
The invention relates to an illumination system for a microlithographic projection equipment, a REMA objective, and a process for the operation of a REMA objective.
2. Discussion of Relevant Prior Act
An illumination system for a microlithographic projection illumination equipment is known from U.S. Pat. No. 4,851,882, with a simple REMA objective which has a field diaphragm, namely the reticle mask (REMA), on which the reticle with the structured lithographic mask is imaged. A zoom system is provided, mounted in front, in order to insure optimum illumination of the whole REMA diaphragm surface with little loss of light, in the case of reticles with different mask dimensions and correspondingly different aperture measurements of the REMA diaphragm. There are no specific embodiment examples.
Highly developed REMA objectives are described in German Patent Application DE-A 195 48 805 and in the German Patent Application DE 196 53 983.8 of Carl Zeiss. They are suitable for cooperating with zoom-axicon illumination objectives according to European Patent EP-A 0 687 956 of Carl Zeiss, and for an arrangement of the REMA diaphragm at the exit of a glass rod according to U.S. Pat. No. 5,646,715. The cited applications of Carl Zeiss are incorporated by reference into the present application. These all have in common, with the present application, the co-inventor Wangler.
European Patent 0 500 393 B1 describes a microlithographic projection illumination system with variable quadrupole illumination, in which there is provided, between a honeycomb condenser and the reticle mask, an optics with the possibility of adjustment in order to adjust the uniformity of illumination. Since the skilled person is given in this patent only functional optical groups in the nature of block diagrams, but not a specific embodiment example, this disclosure has more of a functional character.
U.S. Pat. No. 5,311,362 describes a microlithographic projection illumination system with variable numerical aperture of the illumination system, in which the numerical aperture of the projection objective is also variable and an optical path length between lenses of the projection objective can be varied in dependence on the two numerical apertures, whereby aberrations, primarily the vertical spherical aberration, are corrected.
In general, various embodiments of projection objectives with adjusting means for the correction of variable imaging errors are known.